What ports can be blocked to stop chat rooms and instant messaging?

[Bevan Bennett]

Ernest L. Williams Jr. wrote:

>Hi
>
>Which port does one block to stop all AIM and chat room related network
>activity from going in or out?
>  
>
I don't know which ports modern IM/chat software uses, but these will 
make for a good start:

[bevan at vyvyn ~]$ grep irc /etc/services
irc             194/tcp                         # Internet Relay Chat
irc             194/udp
ircs            994/tcp
ircs            994/udp
ircd            6667/tcp                        # Internet Relay Chat
ircd            6667/udp                        # Internet Relay Chat

Of course, if you can, it's easier and better to block all ports that 
you aren't actively using.